Catalytic reactors are known which comprise an inlet, an outlet, a reactor chamber and a monolithic structure. The monolithic structure is placed within the reactor chamber and a catalytic material is coated on the monolithic structure.
FIG. 1 is a cutaway view of one prior art reactor 100. An example may be found in FIG. 3 of U.S. Pat. No. 5,330,728 to Michael Foster.
The reactor comprises primary channel walls 102 of the monolith and reactor chamber walls 104. The primary channel walls are parallel to each other and to the reactor walls. The primary channel walls form primary channels 103.
The primary channel walls form a monolithic structure wherein each primary channel has a square cross section.
The primary channel walls are coated with a catalyst.
In operation, reactant fluid 110 is caused to flow into the primary channels, react with the catalysts on the primary channel walls and then exit. As used herein unless otherwise specifically indicated or indicated by context, double line arrows indicate fluid flow.
One of the disadvantages of this prior art is that no means is provided to mix the fluids entering different primary channels. Thus if one channel gets a high flow 122 of fluid, said fluid will have a short residence time and hence less reaction with the catalyst than the average fluid. Similarly, if one channel gets a low flow 124 of fluid, then it will have more reaction with the catalyst than the average fluid. Thus a reactor may have to be oversized to account for the difference in fluid flows through different channels.
Another disadvantage of this prior art is that fluids often form a laminar flow as they pass down the primary channels. Thus the fluid 150 passing down the center of a primary channel will have a higher velocity and lower residence time than the fluid 154 passing down next to the walls of the channel. Thus a reactor may have to be oversized to account for the different fluid residence times of the laminar flows near the walls and near the center of primary channels.
Furthermore, this prior art has no means of convective heat transfer from the center of the monolith to the reactor walls.
FIG. 2 is a cutaway view of alternate prior art reactor design 200. An example of this prior at is illustrated in FIG. 2 of U.S. Pat. No. 5,051,241 to William Pfefferle.
The reactor comprises primary channel walls 202 and reactor walls 204. The primary channel walls are parallel to each other and traverse the reactor. The primary channel walls form primary channels 203. Both ends of all of the primary channels are blocked by the reactor walls.
Secondary channels 206 are provided in the primary channel walls to allow inlet fluid 210 to pass therethrough.
Primary channel walls may be a woven wire mesh where the secondary channels are the openings in the mesh. Catalyst is deposited on the walls of the wire forming the wire mesh. Catalyst thus coats both the primary channel walls and the secondary channel walls.
One of the disadvantages of this prior art is that there is a relatively high pressure drop as fluid proceeds from one primary channel wall to the next primary channel wall.